Consumer and commercial appliances have long used program selector switches mounted on a front panel of an appliance that is accessible by the customer. Typically, these selector controls have taken the form of rotary switches, which utilize a cam and follower mechanism or other similar electromechanical device, for varying the operation of the appliance. The manufacturing costs of such electromechanical timers have been reduced regularly in recent decades, while new controls and functions have been added. In a typical application, a user rotates the selector switch to a given program indicated on the front panel of the appliance, thereafter beginning operation of the selected program. In the past, a simple timer mechanism rotated the cam and follower assembly to electromechanically control the operation of the appliance.
Various attempts to substitute electronic controls have failed due to inadequate reliability and operating environment limitations, and especially, to unfavorable cost comparisons with the mechanical cam/switch controls. The advent of reliable and inexpensive control electronic devices, along with other improvements disclosed herein have made possible the implementation of these more advanced electronics to control the program operation of many appliances. Such electronics can effectively replace the older electromechanical cam type devices for program timing, switching, and selection.
FIG. 2 illustrates in simplified form, an electronic control panel installed in an appliance. As may be seen, a prior art electronic control board 10 having a connector 12 included therewith interfaces with a program selector switch 14 through a wiring harness 16 having at the end thereof a connector 18. The program selector switch 14 is typically mounted on an appliance front panel 20 via various mechanisms. Recently, selector switches 14 have begun to implement a simple twist lock mounting mechanism which allows the selector arm portion to be inserted through a mounting hole, such as mounting hole 22, on the appliance front panel 20. The selector switch 14 implementing such a twist lock mechanism is then rotated through a given angle to lock the switch in place on the front panel 20. A selector switch knob (not illustrated) is then inserted on the control arm of the switch.
In addition to the mounting of the selector switch 14, the prior art control board 10 is also mounted within the appliance. Typically, the prior art control board 10 was mounted via mounting screws and insulated spacers 24 on the frame of the appliance. The particular location of the control board 10 often proved difficult due to the limitation on the available space within the appliance. Service requirements also dictated that the front panel 20 be removable from the appliance, such as for maintenance operations or the like. This necessitated a lengthy wiring harness 16 to interface between the front panel mounted switch 14 and the frame mounted control board 10. Because most appliance structures are of sheet metal construction, there exist many sharp edges from stamping operations within the interior of the appliance behind the front panel 20. These sharp edges caused chaffing of the insulation of the wiring harness 16 and the potential for extremely hazardous short-circuiting of the power and/or control wires contained therein.
To overcome this problem, some prior designs utilized wiring harnesses 16 that were as short as possible. Unfortunately, this approach greatly increased the difficulty of maintaining a connection between connectors 12 and 18 during and after servicing of the appliance when the front panel 20 was removed. In addition to the problems associated with decreased reliability and increased difficulty of servicing, the prior systems also bore an increased cost over their predecessors. This increased cost was driven in part by the increased number of components required to make the connection between the panel mounted selector switch 14 and the control board 10. Additionally, the necessary mounting bracket included within the appliance to allow the control board 10 to be mounted thereto also increased the overall cost of this electronic control. The increased costs and reduced reliability has greatly impacted the widespread implementation of this technology over its predecessor electromechanical technology. Because of this impact, electromechanical selector switches are still widely found in many appliances.